The present invention relates to an optical filter comprising a transparent support and a filter layer. In detail, the invention relates to an optical filter used in a display device such as a plasma display panel (PDP), a liquid crystal display device (LCD), an electroluminescence display (ELD), a fluorescent indicator tube or a field emission display to improve the color reproducibility and to prevent the device from causing faulty working of remote-controlled apparatus.
A display device such as a liquid crystal display device (LCD), a plasma display panel (PDP), an electroluminescence display (ELD), a cathode-ray tube (CRT), a fluorescent indicator tube or a field emission display displays a color image with a combination of the three primary colors (i.e., red, blue, green). However, it is very difficult (practically impossible) to use the ideal three primary colors. For example, the plasma display panel uses phosphors of the three primary colors, which emit light containing an unnecessary component (in the wavelength region of 560 to 620 nm). Therefore, it has been proposed to correct the color balance of the displayed image by an optical filter absorbing the unnecessary component. The optical filter for the color correction is described in Japanese Patent Provisional Publication Nos. 58(1983)-153904, 61(1986)-188501, 3(1991)-231988, 5(1993)-205643, 9(1997)-145918, 9(1997)-306366 and 10(1998)-26704.
Further, it has been reported that infrared rays (mainly in the wavelength region of 750 to 1,100 nm) emitted from the display device may cause faulty working of remote-controlled apparatus. For solving this problem, an infrared rays-absorbing filter is used. Dyes used in the infrared rays-absorbing filter are described in U.S. Pat. No. 5,945,209.
An object of the present invention is to provide an optical filter selectively removing both infrared rays and light lowering the color purity of displayed images.
Another object of the invention is to provide a plasma display panel which gives corrected color balance and which is prevented from causing faulty working of remote-controlled apparatus.
The present invention provides an optical filter which comprises a transparent support and at least one filter layer, wherein the optical filter has an absorption maximum in the wavelength region of 560 to 620 nm and another absorption maximum in the wavelength region of 700 to 1,200 nm.
The invention also provides a plasma display panel having a display surface covered with an optical filter, wherein the optical filter comprises a transparent support and at least one filter layer, said optical filter having an absorption maximum in the wavelength region of 560 to 620 nm and another absorption maximum in the wavelength region of 700 to 1,200 nm.
The invention further provides a plasma display panel having a display surface covered with an optical filter, wherein the optical filter comprises a transparent support, a first filter layer and a second filter layer, said first filter layer having an absorption maximum in the wavelength region of 560 to 620 nm, and said second filter layer having an absorption maximum in the wavelength region of 700 to 1,200 nm.